Materials with tunable electrical conductivities can be used for many applications such as switching, storage, and sensing devices. Compared to inorganic materials, organic materials offer a number of advantages including easier processing and integration for large area electronics, lower cost, and better physical flexibility. Polymer nanocomposites, formed by mixing polymers with various types of nanoparticles, have been extensively investigated for many applications. The electrical conductivities of polymer nanocomposites containing conductive nanoparticles typically decrease with temperature and often exhibit a sharp drop near the polymer melting points. Beyond the polymer melting points, the electrical conductivities of the nanocomposites typically increase with temperature. (See, Tjong, S. C., Electrical Properties of Polymer Nanocomposites. In Polymer Composites with Carbonaceous Nanofillers, Wiley-VCH Verlag GmbH & Co. KGaA: 2012; pp 193-245.) While many studies have clearly demonstrated that electrical conductivities of certain polymer nanocomposites can be regulated via temperature, there are a number of limitations to these nanocomposites, including the following: (1) drastic conductivity changes occur near the melting temperatures of the polymers thereby limiting their application due to potential leakage problems; (2) electrical conductivity is typically lower at elevated temperatures; (3) reversible change of electrical conductivity is difficult to harness reproducibly; and (4) for certain applications, it may be impossible or less desirable to achieve direct temperature control using thermal devices, such as an oven or hot plate, making it necessary to employ remotely-controlled photosensitive materials.
Infrared (IR) sensing provides attractive applications in the field of optoelectronics, such as thermography, night vision, medical imaging, and surveillance. There have been previous studies on IR photoresponsive carbon nanotubes (CNTs) and CNT/polymer nanocomposites, in which the IR-induced response in electrical conductivity was mainly attributed to the photoexcitation of CNTs producing extra charge carriers and/or the thermal effect causing a change of CNT conductivity. However, these materials often exhibit relatively low IR sensitivities and inadequate physical flexibility, and may require complex fabrication processes that tend to hinder their potential applications.